The field of the present invention is brake devices for vehicles such as motorcycles and automobiles, and more particularly brake devices provided with an antilock control system.
Antilock brake devices have been developed which include a sensor having a flywheel driven by the vehicle wheel through a transmission to sense the possible onset of wheel lock during braking. The sensor operates by means of an overrunning rotation of the flywheel relative to the vehicle wheel which generates an output signal. Also included is a hydraulic pump driven by the vehicle wheel, also through a transmission. A modulator having a hydraulic control chamber in communication with an output chamber of the hydraulic pump is provided in a hydraulic line between the master cylinder and the wheel brake of the vehicle. This hydraulic control chamber reduces and restores hydraulic pressure to the wheel brake in response to reductions and increases in pressure in the hydraulic control chamber. A normally closed pressure discharge valve is provided in a passage between the hydraulic control chamber and an oil reservoir. The discharge valve is adapted to open upon receipt of an output signal from the sensor. Such a brake device disclosed, for example, in Japanese Patent Application laid-open No. 120,440/1981, in which the whole antilock control device is mounted on a wheel support system for a vehicle externally of the supported wheel.
In the above described device, a substantial amount of room is required externally of the wheel to accommodate the antilock control device. A special support structure is necessary to firmly support the antilock control device on the vehicle. Since the transmission and the sensor are disposed externally of the wheel, various measures have to be specially taken in order to protect them from contamination and injury. In view of the foregoing, such devices exhibit significant disadvantages. Such devices are oversized, complicated, hard to assemble and exhibit instabilities.